'Upbeat' Britney Spears Hits the Dance Studio

With pup London in hand, Britney Spears headed to the Millennium Dance Complex in North Hollywood on Sunday night to work on a new routine, owner Robert Baker tells PEOPLE.

"She is working on the choreography for her song 'Hot as Ice,'" Baker said, "She rehearsed an amazing routine with a chair."

The intense dance session wrapped up a characteristically bizarre weekend, during which Spears invited two photographers back to her home for some late-night champagne. "She was very sweet," said one of the photographers, adding that Spears pal Sam Lutfi claimed to have "filed a restraining order" against Adnan Ghalib.

Ghalib, the paparazzo who has been Spears's near-constant companion in recent weeks, shot back, "I am only now becoming aware of what is being said. I hope to be back home in Los Angeles soon and to be in contact with Miss Spears." (The L.A. police and sheriff's departments both said no emergency protective order had been issued.)

Spears, 26 – who also dropped by PetCo Sunday afternoon, picking up a birdcage and some dog food – spent nearly three hours working on her moves at Millennium. She emerged at 9:30 p.m. in a white top and Dolce and Gabbana sunglasses, chatting with paparazzi and requesting the presence of Filipe, one of the photographers who had been at her home earlier.

"Britney was in an upbeat mood," Baker said, adding that despite the impressive workout, the singer still seemed slightly scatterbrained. "I let her use my personal copy of Blackout. She forgot her own CD."